Thanks for posting this DIY! I was well written and explained the procedure perfectly. As a side note, the Bentley repair manual makes no mention of how to perform this procedure (I was looking for the bolt torque specs).
I just did this yesterday on my '06 325i. I was able to get the bolt near the manifold by using a 1/4-drive Craftsman 8MM socket on a universal joint with a 6" extension bar. I think the procedure is easier with removing the coolant hose, but it's not necessary. Also, Brake Clean did not get all the residue of the old gasket off the head-side of the interface (it wasn't as smooth as I thought it should be). I ended up using some mag wheel polish to get the surface almost back to new.
My coolant did have little black particles in it too. Since my coolant was only 6 months old I re used it. I found the particles when straining the coolant before adding it back in.
As far as the bolt torque goes, as the OP said, just tighten them down in a criss-cross patern until the stop. The purpose is to flaten-out the new gasket.